The present invention relates to the art of power transmission and electronic communication. Particular application is found in the concurrent transmission of electrical power and control signals to undersea and other remote installations and the invention will be described with particular reference thereto. It is to be appreciated, however, that the invention is also applicable for supplying power and communication signals to remote, relatively inaccessible, under fluid, downhole, or like locations.
Heretofore, various techniques have been used for concurrently providing power and communications to undersea and other remote locations. Commonly, separate electrical lines in a cable were used to convey electrical power and control signals.
To ensure safe interconnection and disconnection under water, inductive couplers were provided for transferring electrical power and control signals between the undersea apparatus and the cable. Conventionally, low frequency AC power voltages were transmitted from the surface along the electrical cable to the undersea inductive coupling. Higher frequency control and communication signals were transmitted concurrently along communication lines and across high frequency inductive couplers. However, inductive couplers for lower frequency AC power voltages required a relatively large transformer core for efficient power transfer. The commonly used laminated steel coupler cores were subject to corrosion, particularly by salt water. Although coatings or non-magnetic corrosion-resistant barriers could be applied to inhibit corrosion, they also increased the gap between coupler halves and diminished energy transfer efficiency.
One method for overcoming this shortcoming was to transmit high frequency AC power voltages along the power transmission cables and across the inductive coupler. Inductive coupler for high frequency signals oftentimes used ferrite pot cores which were relatively small and relatively immune to salt water corrosion. The higher the signal frequency, the smaller the core required to transmit a given power level. However, high frequency power transmission causes crosstalk on the high frequency communication lines. Further, high frequency power transmissions attenuated more quickly than lower frequency transmissions, rendering them disadvantageous for long distance power transfer and communication.
The present invention provides an improved electrical power and data signal transmission system which overcomes the above-reference disadvantages and others.